1. Technical Field
The embodiments herein generally relate to television receivers, and, more particularly, to analog television receivers.
2. Description of the Related Art
Analog television encodes television picture and sound information and transmits it as an analog signal in which the message conveyed by a broadcast signal is a function of deliberate variations in an amplitude and/or frequency of the signal. All systems preceding digital television, such as NTSC, PAL, or SECAM are analog television systems. Séquentiel couleur à mémoire (SECAM) (Sequential Color with Memory) is a standard for analog color television systems that is also compatible with monochrome television receivers predating its introduction. Because of this compatibility requirement, a second signal is added to the basic monochrome signal, and this signal carries the color information, called chrominance or C for short.
In National Television System Committee (NTSC), chrominance is encoded using two 3.579545 MHz signals that are 90 degrees out of phase, known as I (in-phase) and Q (quadrature) quadrature amplitude modulation (QAM). These two signals are each, amplitude modulated and then added together. Phase Alternating Line (PAL) is another standard for color television broadcasting. In this standard, the color information on the video signal is reversed with each line. A vestigial sideband (VSB) is a sideband that has been only partly cut off or suppressed. Television broadcasts (in analog video formats) use this method if the video is transmitted in AM, due to the large bandwidth used. Sigma-Delta modulation is a method for encoding high resolution signals into lower resolution signals using pulse-density modulation. An analog-to-digital converter (ADC) or digital-to-analog converter (DAC) circuit, which implements this technique can relatively easily achieve very high resolutions while using low-cost complementary metal-oxide-semiconductor (CMOS) processes, such as the processes used to produce digital integrated circuits (ICs).
Traditional digital front-end architecture for television receivers may include an amplitude imbalance correction (ACI) circuit and a phase imbalance correction (PIC) circuit, however, the PIC is generally always placed only after the ACI. In a traditional television, VSB filtering is performed generally only at an intermediate frequency (IF) stage. Finally, in most of the traditional designs, the front-end architectures typically only use analog circuits for processing.